A number of polymeric systems have been investigated with the view of providing light-weight, high-temperature composites and adhesives for aircraft and aerospace structural applications. However, the matrix and adhesive resins that have been developed are subject to certain limitations. In general, the aliphatic systems have limited use temperatures because of their poor thermooxidative stability and moisture sensitivity. Although certain aromatic and aromatic-heterocyclic systems are moisture insensitive, they are limited by their poor processing parameters.
The principal processing problem inherent in a substantial number of aromatic and aromatic-heterocyclic systems is the absence of an effective method for curing the systems. High temperatures are necessary because extensive flow is mandatory for curing such resins by interchain chemical reactions. Because of their inherent rigidity, aromatic and aromatic-heterocyclic resins are much more susceptible to mobility dependence than are aliphatic resins. There is a need, therefore, for an entirely different method of cure which is not dependent upon extensive molecular mobility. Instead of systems that cure by interchain reactions, which require extensive mobility, improved systems are sought that cure by intramolecular reactions which require only rotational movement of the polymer backbone.
It is a principal object of this invention, therefore, to provide novel diamino aromatic monomers containing phenylethynyl pendant groups which cyclize and cure intramolecularly after polymerization. Other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the accompanying disclosure.